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AGe0.976Sn0.024 n+/p diode was formed using phosphorus ion (P+) implant and rapid thermal annealing at 400°C. Activation of P in Ge typically requires high temperatures (e.g., 700°C), and it was found that this is not needed in the presence of a small amount of Sn. A high forward bias current of 320 A/cm2 at -1 V is achieved for the Ge0.976Sn0.024n+/p diode. This is four times higher than that of the Ge n+/p control diode, which received the same P+ implant but activated at 700°C. The n+-GeSn region has a high active dopant concentration of 2.1 × 1019× cm-3, much higher than that in the Ge control. The increased active dopant concentration in GeSn reduces the width of the tunneling barrier between the Al contact and the n+-GeSn and increases the forward bias diode current. Enhancement of P activation in Ge0.976Sn0.024 could possibly be as a result of passivation of vacancies in the Ge lattice due to Sn atoms.
Date of Publication: Nov. 2012